324. MR. A. S. HORNE ON THE STRUCTURE AND 
zone. The expansion of the narrow cylinder of meristem, increasing in size 
mainly by cell-division in transverse or obliquely transverse planes, causes 
considerable increase in length over girth during cell-enlargement, and has 
a dragging effect on the non-meristematic cells, so that previously transverse 
cortical rows arch downwards as if they had been drawn down toward the axial 
cylinder, and the seed becomes almond-shaped. The vascular bundle branches 
considerably; the fine capillaries, which do not penetrate inward, end in the 
abraphal side. 
9. During the development of the primary embryo the old antipodal system 
disappears. The cells of the internal epidermis are organized into a definite 
epithelium which forms a means for supplying the sac uniformly with nutritive 
material, after the manner described by Billings for the Caprifoliacez. The 
extra-nucellar tissue forms a kind of water-jacket, the inner cells of which (inner, 
meristematic zone) function as collecting-cells. 
10. True endosperm is present as a thin-walled tissue in very young stages of the 
primary embryo. Owing to intermittent division of the endosperm cells and 
the general elongation of the sac, the outline of the cells is irregular. 
11. The upper cells of the young pro-embryo function as a temporary absorbent organ, 
leaving a bulbous cavity in the endosperm when they disappear. By this time 
the true embryo begins to develop at the end of the suspensor as a small undif- 
ferentiated mass of cells, and later takes upon itself the absorptive function of 
the suspensor. 
12. The fruit. at the time of germination consists of an exceedingly hard stony 
endocarp formed by the extreme sclerosis of all the ovarian tissue within, and 
including that of the inner peripheral cylinder of bundles. Dehiscence takes 
place by the removal of the upper part of the back of each chamber. The seeds 
are enveloped in a brown, scaly testa, which is all that remains of the extra- 
nucellar tissue. 
18. The embryo gradually absorbs the endosperm by means of its epidermal layer, 
which, at the time, functions as a secretory epithelium. During germination 
the radicle emerges from the endosperm in the manner described by Hemsley. 
14. From a detailed study of the flowers, ovary, ovule, and seed, the author is inclined | 
to believe that Davidia has no real affinity with the Hamamelidacee, but is | 
distantly related to Alangium and Nyssa, and still more distantly related to the 
Araliacee: that the genus occupies a more isolated position than has hitherto 
been supposed, owing to having pursued an independent course of development 
from the plexus of primitive groups which included the ancestral forms of the 
Araliaceze, Nysseæ, and Alangiere. 
I desire to express my heartfelt thanks to Professor J. B. Farmer for having placed | 
his material of Davidia at my disposal for the purposes of this research, and for his | 
continual help and encouragement. 
